This invention relates to a process for preparing halocarbonylbis(triorganophosphorus) rhodium compounds and to a process for preparing hydridocarbonyltris(triorganophosphorus) rhodium compounds directly from said halocarbonylbis(triorganophosphorus) rhodium compounds. More particularly this invention relates to an organic one-phase process for preparing halocarbonylbis(triorganophosphorus) rhodium compounds from an organic concentrate of a spent hydroformylation reaction medium and to a process for preparing hydridocarbonyltris(triorganophosphorus) rhodium compounds directly from said halocarbonylbis(triorganophosphorus) rhodium compounds so produced without isolating such halo-containing rhodium compounds from their product mixture.
Organic one-phase processes for preparing halocarbonylbis(triorganophosphorus) rhodium compounds from simple rhodium chloride monomeric compounds are known in the art, e.g. J. A. McCleverty et al. "Inorganic Syntheses", Vol. 8, page 214 (1966) and D. Evans et al. "Inorganic Syntheses", Vol. XI. pp. 99 to 101 (1968) disclose reacting rhodium trichlorohydrate (RhCl.sub.3.3H.sub.2 O) with formaldehyde and triphenylphosphine in the presence of an organic solvent to produce chlorocarbonylbis(triphenylphosphine) rhodium. However, methods for preparing halocarbonylbis(triorganophosphorus) rhodium compounds from distillation residues of rhodium catalyzed hydroformylation processes are much more difficult and heretofore have involved aqueous phase type transfer processes wherein the reaction is conducted in the presence of an aqueous solution.
For example U.S. Pat. No. 4,021,463 discloses a process for preparing halocarbonylbis(triorganophosphine) rhodium by treating the distillation residue of a hydroformylation mixture with an aqueous mineral acid and a peroxide to convert the rhodium into its water-soluble salt which passes into the aqueous phase, mixing the resulting aqueous salt solution with a solvent, tertiary phosphine and hydrohalic acid or metal halide and reacting the aqueous solution with carbon monoxide or a carbon monoxide donor. Said patent further discloses that hydridocarbonyltris(triorganophosphine) rhodium can be produced by simultaneously subjecting the aqueous starting solution to hydrogenation conditions or by subjecting a solvent solution of the halo-containing compound product together with additional phosphine to hydrogenation conditions.
U.S. Pat. No. 4,113,754 discloses a process for preparing chlorocarbonylbis(triorganophosphine) rhodium compounds by treating a distillation residue of a hydroformylation mixture with oxygen containing mineral acids and peroxides to form an aqueous rhodium salt solution which is then treated with a cation exchanger and the latter separated from the solution. The absorbed rhodium ions are deabsorbed with hydrochloric acid and the hexachlororhodate solution containing HCl then reacted in the presence of a water-soluble organic solvent, a tertiary phoshine and carbon monoxide to produce the desired product. The patent further discloses that if the process is carried out under hydrogenation conditions that hydridocarbonyltris(triorganophosphine) rhodium is produced.
U.S. Pat. No. 3,968,134 discloses a process for preparing chlorocarbonylbis(triorganophosphine) rhodium compounds by treating a raw hydroformylation product, or the tails of a distillation of same containing a triorganophosphine ligand with an aqueous solution of an aldehyde and a strong acid (e.g. HCl), obtaining the desired rhodium product by filtration and separating the aqueous solution containing triorganophosphine by decantation.